This nonprovisional application claims priority under 35 U.S.C. xc2xa7119(a) on Patent Application No. 2001-118961 filed in Japan on Apr. 18, 2001, which is herein incorporated by reference.
The present invention relates to a pressing apparatus, and particularly to a pressing apparatus exerting a pressing force only near the lower dead center of the pressing stroke where the pressing force is mostly needed.
When bending a work by means of a cam die for example, assume that there is an 85 mm pressing stroke. Within this 85 mm of the pressing stroke, it is only about 25 mm portion near the end of the pressing stroke, i.e. near the lower dead center of the pressing apparatus, that is used directly for bending the work. It is this ending portion of the pressing stroke that requires a large pressing force for bending operation for example.
The slide cam is urged by a pressing-urge provider, which is generally provided by a coil spring. In order to exert a large urging force near the ending portion of the pressing stroke, an initial spring pressure must also be set at a high level of spring pressure.
Because of this setting, the slide cam, a slide cam base and a sliding portion of a driven cam are subject to abnormal wear and seizure.
Another problem is that during a preparatory step before manufacture, a few design changes are usually made to the pressing apparatus. In such occasions for example, it is required that the slide cam, the slide cam base, the driven cam and so on should be disassembled and reassembled easily, with the pressing apparatus staying installed to the pressing machine.
With the circumstances described above, it is an object of the present invention that the urging force for the slide cam to press is provided only when necessary and this pressing-urge is held as small as possible in a portion of the pressing stroke in which the work is not directly pressed, thereby preventing abnormal wear and seizure of the slide cam, slide cam base and the sliding portion of the driven cam. The present invention provides a pressing apparatus comprising: a slide cam base; a slide cam slidably provided in a guidepost attached to the slide cam base, the slide cam holding a pressing member such as a bending member and being guided by the slide cam base; a retracting-urge provider provided between the slide bas base and the slide cam for urging the slide cam; and a driven cam for contacting and driving the slide cam; wherein a pressing-urge provider for urging the slide cam only near a lower dead center of a pressing stroke is provided between the slide cam base and the slide cam and/or between the slide cam and the driven cam.
Further, in order to enable disassembling and reassembling of the slide cam, the slide cam base and the driven cam with the pressing apparatus staying installed to a pressing machine, the present invention provides a pressing apparatus, wherein the guidepost has an end formed with a threaded hole and each of the retracting-urge provider and the pressing-urge provider are mounted on a mounting plug faced by a wall formed with a through hole, thereby enabling the disassembling and reassembling of the slide cam, with the pressing apparatus remaining installed to the pressing machine.